Map information processor and data structure of map information

ABSTRACT

A map information processor includes a map information storage unit  13  for storing map display information including a set of pieces of mesh-by-mesh map information managed on a mesh-by-mesh basis and including road information, background information, and in-mesh image information, an image processing unit  15  for generating a map image on a basis of image data included in the road information, the background information, and the in-mesh image information included in the mesh-by-mesh map information read from the map information storage unit, and a display device  5  for displaying the map image generated by the image processing unit.

FIELD OF THE INVENTION

The present invention relates to a map information processor thatprocesses map information in, for example, a car navigation device, andthe data structure of map information for use in this map informationprocessor.

BACKGROUND OF THE INVENTION

In a conventional map information processor, image data showing alandmark to be displayed on a map such as a facility is managed in theoutside of meshes independently from data managed on a mesh-by-meshbasis (for example, refer to patent reference 1).

It takes much time to perform a map image generating process whenreferring to required image data every time when generating a map imagefrom such image data managed in the outside of meshes, and theperformance of the map information processor therefore degrades. Tosolve this problem, the conventional map information processor shortensthe time required to perform the map image generating process by readingimage data managed in the outside of meshes into a RAM in advance.

[Patent reference 1] JP,2005-214783,A

However, in a case of handling image data having a data amount exceedingthe capacity of the RAM disposed in the map information processor, asituation in which the map information processor cannot read all theimage data into the RAM occurs. Therefore, there is a demand toimplement map image generation in a short time also in such a situation.

The present invention is made in order to meet the above-mentionedrequest, and it is therefore an object of the present invention toprovide a map information processor that can shorten the time requiredto perform a map image generating process.

DISCLOSURE OF THE INVENTION

In order to solve the above-mentioned problems, a map informationprocessor in accordance with the present invention includes: a mapinformation storage unit for storing map display information including aset of pieces of mesh-by-mesh map information managed on a mesh-by-meshbasis and including road information, background information, andin-mesh image information; an image processing unit for generating a mapimage on a basis of image data included in the road information, thebackground information, and the in-mesh image information included inthe mesh-by-mesh map information read from the map information storageunit; and a display unit for displaying the map image generated by theimage processing unit.

Because the map information processor in accordance with the presentinvention can generate a map image on the basis of only image dataincluded in in-mesh image information managed on a mesh-by-mesh basis,the map information processor in accordance with the present inventiondoes not have to read image data managed in the outside of meshes.Therefore, the map information processor in accordance with the presentinvention can shorten the time required to perform a map imagegenerating process.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram showing the structure of a car navigationsystem to which a map information processor according to Embodiment 1 ofthe present invention is applied;

FIG. 2 is a view showing the data structure of map information for usein the map information processor in accordance with Embodiment 1 of thepresent invention;

FIG. 3 is a view showing the detailed data structure of map displayinformation shown in FIG. 2;

FIG. 4 is a view showing the detailed data structure of the imageinformation shown in FIG. 2;

FIG. 5 is a view showing the detailed data structure of in-mesh imageinformation shown in FIG. 3;

FIG. 6 is a flow chart showing the operation of the map informationprocessor in accordance with Embodiment 1 of the present invention,focusing on a map image generating process;

FIG. 7 is a view for explaining a process of specifying a mesh which iscarried out in the map image generating process by the map informationprocessor in accordance with Embodiment 1 of the present invention;

FIG. 8 is a flowchart showing the details of a process of drawing pointinformation which is carried out in the map image generating process bythe map information processor in accordance with Embodiment 1 of thepresent invention;

FIG. 9 is a view showing the structure of point data of map informationfor use in a map information processor in accordance with Embodiment 2of the present invention;

FIG. 10 is a flow chart showing the details of a process of drawingpoint information which is carried out by the map information processorin accordance with Embodiment 2 of the present invention;

FIG. 11 is a view showing the configuration of a priority determinationtable for use in the map information processor in accordance withEmbodiment 2 of the present invention;

FIG. 12 is a view showing the configuration of map display informationof map information for use in the map information processor inaccordance with Embodiment 3 of the present invention;

FIG. 13 is a flow chart showing the details of a process of drawingpoint information which is carried out in a map image generating processby the map information processor in accordance with Embodiment 3 of thepresent invention;

FIG. 14 is a view for explaining a process of specifying mesh-by-meshmap information in an upper layer which is carried out by the mapinformation processor in accordance with Embodiment 3 of the presentinvention; and

FIG. 15 is a view showing the detailed data structure of in-mesh imageinformation for use in a map information processor in accordance with avariant of Embodiment 3 of the present invention.

PREFERRED EMBODIMENTS OF THE INVENTION

Hereafter, a preferred embodiment of the present invention will bedescribed with reference to the accompanying drawings.

Embodiment 1

FIG. 1 is a block diagram showing the configuration of a car navigationsystem to which a map information processor in accordance withEmbodiment 1 of the present invention is applied. This navigation systemis provided with a remote controller (abbreviated as a “remote control”from here on) light receiving device 1, a velocity sensor 2, a GPS(Global Positioning System) receiving antenna 3, an angular velocitysensor 4, a display device 5, a voice output device 6, and a carnavigation device 7.

The remote control light receiving device 1 receives a signal (aninfrared ray or a radio wave) for commanding an operation which is sentthereto from a wireless remote control (not shown) operated by a user,and sends an operation signal, as the signal, to the car navigationdevice 7.

The velocity sensor 2 measures the velocity at which the car navigationsystem itself is travelling, and sends a velocity signal, as thevelocity, to the car navigation device 7. The GPS receiving antenna 3receives radio waves transmitted from GPS satellites, and sends GPSsignals, as the radio waves, to the car navigation device 7. The angularvelocity sensor 4 measures a change in the direction of the carnavigation system itself, and sends a direction signal, as the change,to the car navigation device 7.

The display device 5 consists of, for example, a liquid crystal display,and displays information including a map image or an optimal routeaccording to an image signal sent thereto from the car navigation device7. The voice output device 6 consists of, for example, a speaker, andoutputs a voice to provide guidance to a destination along the optimalroute according to a voice signal sent thereto from the car navigationdevice 7. The voice output device 6 outputs, via voice, informationincluded in map information.

The car navigation device 7 is provided with a user's operation inputunit 11, a sensor information input unit 12, an HDD (Hard Disk Drive)13, a RAM (Random Access Memory) 14, a navigation processing unit 15, anoutput control unit 16, and a control unit 17.

The user's operation input unit 11 receives the operation signal sentthereto from the remote control light receiving device 1, and sends theoperation signal to the control unit 17. The sensor information inputunit 12 receives the vehicle velocity signal sent thereto from thevelocity sensor 2, the GPS signals sent thereto from the GPS receivingantenna 3, and the direction signal sent thereto from the angularvelocity sensor 4, and sends sensor information, as these signals, tothe control unit 17. The control unit 17 detects the position of the carnavigation system itself on the basis of these vehicle velocity signal,GPS signals, and direction signal.

The HDD 13 corresponds to a map information storage unit according tothe present invention, and stores map information. The details of themap information will be mentioned below. This map information stored inthe HDD13 is read by the control unit 17. The map information storageunit according to the present invention is not limited to the HDD. Forexample, a recording medium, such as a DVD (Digital Versatile Disk) orCD (Compact Disc), and a drive for driving this recording medium can beused as the map information storage unit.

The RAM 14 stores temporarily data used for various processes. Forexample, map information read from the HDD 13 is written in the RAM 14via the control unit 17. The map information stored in the RAM 14 isread by the navigation processing unit 15 via the control unit 17.

The navigation processing unit 15 performs various processes forimplementing navigation functions according to a command from thecontrol unit 17. For example, the navigation processing unit 15 detectsthe current position on the basis of the sensor information from thesensor information input unit 12, and also refers to the map informationstored in the HDD 13 to carry out processes for implementing a currentposition positioning function of determining the position on a roadwhere the current position exists, a map display function of generatinga map image, which is to be displayed on the display device 5, of eitheran area in the vicinity of the current position or an arbitrary point, aroute determining function of determining either an optimal route fromthe current position to an arbitrary point or an optimal route betweenarbitrary points, a route guiding function of providing guidance such asa right turn or a left turn while the vehicle equipped with the carnavigation system travels to the destination along the optimal routedetermined with the route determining function, and so on. Thenavigation processing unit implements each of these functions withreference to the map information stored in the HDD 13. The processresults obtained by this navigation processing unit 15 are sent to thecontrol unit 17. A image processing unit according to the presentinvention is implemented by the navigation processing unit 15.

The output control unit 16 generates an image signal on the basis of theresults of the navigation processing sent thereto, via the control unit17, from the navigation processing unit 15 and sends the image signal tothe display device 5, and also generates a voice signal and sends thevoice signal to the voice output device 6.

The control unit 17 controls the whole car navigation device 7 bycontrolling the user's operation input unit 11, the sensor informationinput unit 12, the HDD 13, the RAM 14, the navigation processing unit15, and the output control unit 16.

Next, the details of the map information stored in the HDD 13 will beexplained. FIG. 2 shows the data structure of the map information. Themap information is comprised of map display information 21 and imageinformation 22. The map display information 21 is comprised of a set ofpieces of mesh-by-mesh map information 31 ₁, 31 ₂, □ . . . , and 31 _(m)(m is a positive integer) which are managed on a mesh-by-mesh basis,i.e., which are managed respectively in grid-shaped meshes into which awhole area for which map display is supported is divided, as shown inFIG. 3( a). Each of the pieces of mesh-by-mesh map information 31 ₁, 31₂, □ . . . , and 31 _(m) (each mesh-by-mesh map information isrepresentedly designated by a numeral reference “31” from here on) iscomprised of road information 41, background information 42, and in-meshimage information 43, as shown in FIG. 3( b).

The road information 41 is comprised of a set of pieces of linkinformation (including coordinate information) each corresponding to aroad. The background information 42 is comprised of surface information51, line information 52 and point information 53. The surfaceinformation 51 is the one for drawing surfaces, such as woods and lakes,and are comprised of a set of surface data each corresponding to anindividual surface. Each surface data holds coordinate information abouta surface. The line information 52 is the one for drawing lines, such asrivers and administrative boundary lines, and is comprised of a set ofline data each corresponding to an individual line. Each line data holdscoordinate information about a line. The point information 53 is the onefor drawing symbols and images, such as facility mark images and mapsymbols, and is comprised of a set of point data 61 each correspondingto an individual symbol or image, or the like.

As shown in FIG. 3( c), each point data 61 holds coordinate information71 showing a position at which an individual symbol, a facility markimage or the like is drawn, a category code 72 which is an identifierfor acquiring image data to be displayed on a map screen from the imageinformation 22, and an image code 73 which is an identifier foracquiring image data to be displayed on the map screen from the in-meshimage information 43.

FIG. 4 shows the data structure of the image information 22. The imageinformation 22 is the one which is not managed on a mesh-by-mesh basis,i.e. map information managed in the outside of the meshes. As shown inFIG. 4( a), the image information 22 is comprised of a set of imagerecords 81 ₁, 81 ₂, . . . , and 81 _(n). Each of the image records 81 ₁,81 ₂, . . . , and 81 _(n) (each image record is representedly designatedby a numeral reference “81” from here on) holds an identifier 91 forspecifying image data uniquely and the image data 92, as shown in FIG.4( b). The image data 92 can be formed using a general format, e.g. abitmap format. Each image data 92 stored in the image information 22 isthe one frequently used in the map display function, e.g. the one usedin a case of producing a map display of an image of either a facilitymark according to the type of a facility (e.g. a mark showing a postoffice) or a map symbol.

FIG. 5 shows the data structure of the in-mesh image information 43. Thein-mesh image information 43 is comprised of a set of image records 101₁, 101 ₂, . . . , and 101 _(n), as shown in FIG. 5( a). Each of theimage records 101 ₁, 101 ₂, . . . , and 101 _(n) (each image record isrepresentedly designated by a numeral reference “101” from here on)holds an identifier ill for specifying image data uniquely and the imagedata 112, as shown in FIG. 5( b). The image data 112 can be formed usinga general format, e.g. a bitmap format. As each image data 112 stored inthe in-mesh image information 43, there can be image data having a lowuse frequency in the map display function, e.g. image data used in acase of producing a map display of an image of a specific facility(Tokyo Disneyland (registered trademark), Tokyo Tower, or the like).

Next, the operation of the map information processor in accordance withEmbodiment 1 of the present invention configured as mentioned above willbe explained with reference to a flow chart shown in FIG. 6 and anexplanatory drawing shown in FIG. 7, focusing on a map image generatingprocess for implementing the map display function.

When the map image generating process is started, meshes required forgeneration of a map image are specified first (step ST1). The navigationprocessing unit 15 selects meshes for an area displayed in a displayarea of the display device 5 to specify the meshes. For example, in acase in which an area shown by a thick frame of FIG. 7 is the displayarea of the display device 5, meshes a, b, c, d, e, and f are specifiedas the required meshes.

Next, pieces of mesh-by-mesh map information 31 respectivelycorresponding to the meshes specified in step ST1 are read into the RAM14 (step ST2). More specifically, the navigation processing unit 15reads the pieces of mesh-by-mesh map information 31 respectivelycorresponding to the meshes specified in step ST1 via the control unit17 from the map display information 21 of the map information stored inthe HDD 13, and stores the pieces of mesh-by-mesh map information in theRAM 14.

Next, in order to draw a map image corresponding to all the pieces ofmesh-by-mesh map information 31 read in step ST2, whether or not thereis one or more yet-to-be-processed pieces of mesh-by-mesh mapinformation 31 is checked to see (step ST3). When it is judged in thisstep ST3 that there is no yet-to-be-processed piece of mesh-by-mesh mapinformation 31, the map image generating process is ended.

In contrast, when it is judged in step ST3 that there is one or moreyet-to-be-processed pieces of mesh-by-mesh map information 31, oneyet-to-be-processed piece of mesh-by-mesh map information is selected asthe target for processing from the one or more yet-to-be-processedpieces of mesh-by-mesh map information 31 (step ST4). More specifically,the navigation processing unit 15 selects one of the one or moreyet-to-be-processed pieces of mesh-by-mesh map information 31 stored inthe RAM 14 as the target for processing via the control unit 17. Whenthe navigation processing unit 15 accesses the RAM 14, the navigationprocessing unit certainly accesses the RAM via the control unit 17.Therefore, the following description “via the control unit 17” will beomitted hereafter in such an explanation.

Drawing according to the surface information 51 of the mesh-by-mesh mapinformation 31 selected in step ST4 which is the target for processingis then carried out (step ST5). More specifically, the navigationprocessing unit 15 reads the surface information 51 of theyet-to-be-processed piece of mesh-by-mesh map information 31 selected instep ST4 from the RAM 14, and performs drawing of a surface such aswoods or a lake according to this read surface information 51.

Drawing according to the line information 52 of the mesh-by-mesh mapinformation 31 selected in step ST4 which is the target for processingis then carried out (step ST6). More specifically, the navigationprocessing unit 15 reads the line information 52 of theyet-to-be-processed piece of mesh-by-mesh map information 31 selected instep ST4 from the RAM 14, and performs drawing of a line, such as ariver or an administrative boundary line, according to this read lineinformation 52.

Drawing according to the road information 41 of the mesh-by-mesh mapinformation 31 selected in step ST4 which is the target for processingis then carried out (step ST7). More specifically, the navigationprocessing unit 15 reads the road information 41 of theyet-to-be-processed piece of mesh-by-mesh map information 31 selected instep ST4 from the RAM 14, and performs drawing of roads according tothis read road information 41.

Drawing according to the point information 53 of the mesh-by-mesh mapinformation 31 selected in step ST4 which is the target for processingis then carried out (step ST8). More specifically, the navigationprocessing unit 15 reads the point information 53 of theyet-to-be-processed piece of mesh-by-mesh map information 31 selected instep ST4 from the RAM 14, and performs drawing based on one-point typedata, such as a facility mark or a map symbol, according to this readpoint information 53. The process carried out in this step ST8 will befurther explained in detail. After that, the sequence returns to stepST3 and the above-mentioned processes are repeated.

FIG. 8 is a flow chart showing the details of the process of drawing thepoint information performed in step ST8. In this process of drawing thepoint information, it is checked to see first whether or not one or moreyet-to-be-processed point data 61 are included in the point information53 (step ST11). More specifically, the navigation processing unit 15refers to the contents of the RAM 14 to check to see whether one or moreyet-to-be-processed point data 61 are included in the point information53 of the yet-to-be-processed mesh-by-mesh map information 31 selectedin step ST4. When it is judged in this step ST11 that noyet-to-be-processed point data 61 are included in the point information53, the process of drawing the point information is ended.

In contrast, when it is judged in step ST11 that one or moreyet-to-be-processed point data 61 are included in the point information53, one of the one or more yet-to-be-processed point data 61 is thenselected as the target for processing (step ST12). More specifically,the navigation processing unit 15 selects, as the target for processing,one of the one or more the yet-to-be-processed point data 61 included inthe point information 53 of the yet-to-be-processed mesh-by-mesh mapinformation 31 stored in the RAM 14.

Image data 112 whose identifier 111 matches the image code 73 of thepoint data 61 selected in step ST12, which is the target for processing,is then searched from among the in-mesh image information 43 (stepST13). More specifically, the navigation processing unit 15 searches forimage data 112 whose identifier 111 of an image record 100 included inthe in-mesh image information 43 of the yet-to-be-processed mesh-by-meshmap information 31 stored in the RAM 14 matches the image code 73 of theyet-to-be-processed point data 61 included in the point information 53of the mesh-by-mesh map information 31.

It is then checked to see whether or not the image data exists (stepST14). More specifically, the navigation processing unit 15 checks tosee whether the image data 112 whose identifier 111 matches the imagecode 73 of the yet-to-be-processed point data 61 included in the pointinformation 53 of the mesh-by-mesh map information 31 has been searchedfrom among all the image records 100 included in the in-mesh imageinformation 43 of the yet-to-be-processed mesh-by-mesh map information31 stored in the RAM 14.

When it is judged in this step ST14 that the image data exists, theimage data 112 is then drawn according to the coordinate information 71of the point data 61 (step ST15). More specifically, the navigationprocessing unit 15 draws an image based on the image data 112, which hasbeen searched from among the in-mesh image information 43 of theyet-to-be-processed mesh-by-mesh map information 31 stored in the RAM14, at the position shown by the coordinate information 71 of the pointdata 61. After that, the sequence returns to step ST11 and theabove-mentioned processes are repeated.

In contrast, when it is judged in step ST14 that the image data does notexist, image data 92 whose identifier 91 matches the category code 72 ofthe point data 61 selected in step ST12, which is the target forprocessing, is searched from among the image information 22 (step ST16).More specifically, the navigation processing unit 15 searches for imagedata 92 whose identifier 91 of an image record 81 of the imageinformation 22 stored in the RAM 14 matches the category code 72 of theyet-to-be-processed point data 61 included in the point information 53of the mesh-by-mesh map information 31.

It is then checked to see whether or not the image data exists (stepST17). More specifically, the navigation processing unit 15 checks tosee whether or not the image data 92 whose identifier 91 matches thecategory code 72 of the yet-to-be-processed point data 61 included inthe point information 53 of the mesh-by-mesh map information 31 has beensearched from among all the image records 81 of the image information 22stored in the RAM 14.

When it is judged in this step ST17 that the image data 92 does notexist, the sequence returns to step ST11 and the above-mentionedprocesses are repeated. In contrast, when it is judged in step ST17 thatthe image data 92 exists, the image data 92 is then drawn according tothe coordinate information 71 of the point data 61 (step ST18). Morespecifically, the navigation processing unit 15 draws an image based onthe image data 92, which has been searched from among the imageinformation 22 stored in the RAM 14, at the position shown by thecoordinate information 71 of the point data 61. After that, the sequencereturns to step ST11 and the above-mentioned processes are repeated.

As previously explained, because the map information processor inaccordance with Embodiment 1 of the present invention can generate a mapimage on the basis of image data included in in-mesh image informationwhich is managed on a mesh-by-mesh basis, the map information processordoes not have to read image data managed in the outside of meshes.Therefore, the map information processor can shorten the time requiredto perform a map image generating process. Furthermore, because the mapinformation processor manages image data about a large number of typesof image data about images having a low frequency of occurrence in a mapwithin the meshes, and manages image data about a small number of typesof image data about images having a high frequency of occurrence in amap in the outside of the meshes, the map information processor canshorten the time required to perform a map image generating processwhile suppressing the capacity of a memory for use in the mapinformation processor.

At the time of startup of the car navigation device 7, the reading ofthe image data 92 included in each image record 81 of the imageinformation 22 into the RAM 14 is completed in advance. As a result,because the operation of searching for image data 92 which is specifiedby an identifier 91 which matches the category code 72 of the point data61 can be implemented with search through the RAM 14 for the image data,the searching operation can be carried out at a high speed.

The above-mentioned map information processor in accordance withEmbodiment 1 is configured in such a way as to store image data 92frequently used in the map display function as the image information 22,and, in the map image generating process, acquire and draw image data 92from the image information 22 according to the category code 72. As analternative, the above-mentioned map information processor can beconfigured in such a way as to store also image data frequently used inthe map display function in the in-mesh image information 43, and, inthe map image generating process, acquire and draw image data 92 fromthe in-mesh image information 43 according to the image code 73.

Furthermore, the map display information stored in the HDD 13 andincluded in the map information can be formed dividedly into pluralpieces of map display information respectively configured in a pluralityof layers according to display densities. In this case, map displayinformation in each of the layers is comprised of a set of pieces ofmesh-by-mesh map information.

Embodiment 2

A car navigation system to which a map information processor inaccordance with Embodiment 2 of the present invention is applied has thesame configuration as that of the car navigation system to which the mapinformation processor in accordance with Embodiment 1 shown in FIG. 1 isapplied, except for the data structure of map information stored in anHDD 13 of a car navigation device 7.

Map information for use in the map information processor in accordancewith this Embodiment 2 is the same as that for use in the mapinformation processor in accordance with above-mentioned Embodiment 1,with the exception that point data 61 a is provided instead of pointdata 61. Hereafter, the difference between this Embodiment andEmbodiment 1 will be explained mainly.

FIG. 9 shows the configuration of each point data 61 a for use in themap information processor in accordance with Embodiment 2. Each pointdata 61 a is configured in such a way as to include a priority 74 inaddition to the elements of each point data 61 as shown in FIG. 3( c).It is assumed that the larger value the priority 74 has the higherpriority is assigned to each point data.

Next, the operation of the map information processor in accordance withEmbodiment 2 of the present invention configured as mentioned above willbe explained. A map image generating process carried out by the mapinformation processor in accordance with this Embodiment 2 is the sameas that carried out by the map information processor in accordance withEmbodiment 1, except for a process of drawing point information which isperformed in step ST8 of the flow chart shown in FIG. 6. Hereafter, onlya part different from that shown in Embodiment 1 will be explained.

FIG. 10 is a flow chart showing the details of the process of drawingpoint information performed in step ST8. In this process of drawingpoint information, step ST21 is added between step ST14 and step ST15 ofthe process of drawing point information shown in the flow chart of FIG.8, which is carried out by the map information processor in accordancewith Embodiment 1. Hereafter, the steps in which the same process asthat of drawing point information in the map information processor inaccordance with Embodiment 1 is carried out are designated by the samereference characters as those used in FIG. 8, and the explanation of thesteps will be simplified.

In the process of drawing point information, it is checked to see firstwhether or not one or more yet-to-be-processed point data 61 areincluded in the point information 53 (step ST11). When it is judged inthis step ST11 that no yet-to-be-processed point data 61 is included inthe point information 53, the process of drawing point information isended. In contrast, when it is judged that one or moreyet-to-be-processed point data 61 are included in the point information53, one of the one or more yet-to-be-processed point data 61 is thenselected as the target for processing (step ST12). Image data 112 whoseidentifier 111 matches the image code 73 of the point data 61 selectedin step ST12, which is the target for processing, is then searched fromamong the in-mesh image information 43 (step ST13).

It is then checked to see whether or not the image data exists (stepST14). When it is judged in this step ST14 that the image data exists,it is then checked to see with reference to the priority 74 and thecoordinate information 71 whether or not the image data is the targetfor drawing (step ST21). More specifically, a navigation processing unit15 determines whether or not the image data is the target for drawingaccording to the coordinate information 71 and the priority 74 of theyet-to-be-processed point data 61 which is included in the pointinformation 53 of the mesh-by-mesh map information 31 by examining allthe image records 100 included in the in-mesh image information 43 ofthe yet-to-be-processed mesh-by-mesh map information 31 stored in theRAM 14.

In this determination, a priority determination table as shown in FIG.11 is used. The priority determination table can be stored and placed inthe HDD 13. As an alternative, a determination rule can be incorporatedinto a program for defining the operation of the navigation processingunit 15 in advance. In this step ST21, from the coordinates of thecenter of a display area of a display device 5, and the coordinateinformation 71 of the point data 61 which is the target for processing,the distance between them is determined, whether or the image data isthe target for drawing is determined from the distance and the graphicalscale of a map image to be generated.

For example, in a case in which the graphical scale of a map drawn bythe navigation processing unit 15 is 500 meters, it is determined thatthe image data is the target for drawing when the priority 74 of thepoint data 61 which is the target for determination is “1” regardless ofthe distance, when the priority 74 of the point data 61 is “2” and thedistance is less than 5 km, and when the priority 74 of the point data61 is “3” and the distance is less than 2 km, whereas it is determinedthat the image data is not the target for drawing when the priority 74of the point data 61 is “4”. When it is judged in this step ST21 thatthe image data is not the target for drawing, the sequence returns tostep ST11 and the above-mentioned processes are repeated.

In contrast, when it is judged in step ST21 that the image data 112 isthe target for drawing, the image data 112 is then drawn according tothe coordinate information 71 of the point data 61 (step ST15). Afterthat, the sequence returns to step ST11 and the above-mentionedprocesses are repeated. In contrast, when it is judged in step ST14 thatthe image data does not exist, image data 92 whose identifier 91 matchesthe category code 72 of the point data 61 selected in step ST12, whichis the target for processing, is searched from among the imageinformation 22 (step ST16).

It is then checked to see whether or not the image data exists (stepST17). When it is judged in this step ST17 that the image data does notexist, the sequence returns to step ST11 and the above-mentionedprocesses are repeated. In contrast, when it is judged in step ST17 thatthe image data 92 exists, the image data 92 is then drawn according tothe coordinate information 71 of the point data 61 (step ST18). Afterthat, the sequence returns to step ST11 and the above-mentionedprocesses are repeated.

As explained above, because the map information processor in accordancewith Embodiment 2 of the present invention is configured in such a wayas to control whether to enable or disable drawing of an objectaccording to its priority, the map information processor can preventreduction in the user's visibility on the map due to display of variousimages on the map image.

The map information processor in accordance with this Embodiment 2 isconfigured in such a way as to, when drawing image data 112corresponding to the image code 73 of the point data 61 which is thetarget for processing, determine whether or not the image data is thetarget for drawing according to the priority determination table. As analternative, the map information processor can be configured in such away as to carry out this determination immediately after selecting thepoint data 61 which is the target for processing.

Embodiment 3

A car navigation system to which a map information processor inaccordance with Embodiment 3 of the present invention is applied has thesame configuration as that of the car navigation system to which the mapinformation processor in accordance with Embodiment 1 shown in FIG. 1 isapplied, except for the data structure of map information stored in anHDD 13 of a car navigation device 7.

Map information for use in the map information processor in accordancewith this Embodiment 3 is the same as that for use in the mapinformation processor in accordance with above-mentioned Embodiment 1,with the exception that the map information for use in the mapinformation processor in accordance with this Embodiment 3 is formeddividedly into plural pieces of map information respectively configuredin a plurality of layers according to display densities. Hereafter, thedifference between this Embodiment and Embodiment 1 will be explainedmainly.

FIG. 12 shows the data structure of map display information 21 for usein the map information processor in accordance with Embodiment 3. Themap display information 21 is comprised of a multiple-layered set ofpieces of map display information 23 ₁, 23 ₂, . . . , and 23 _(n)respectively corresponding to the plurality of layers divided accordingto display densities. Each of the pieces of map display information 23₁, 23 ₂, . . . , and 23 _(n) in the multiple-layered set (each mapdisplay information is representedly designated by a numeral reference“23” from here on) is comprised of a set of pieces of mesh-by-mesh mapinformation 31 ₁, 31 ₂, . . . , and 31 _(n) managed on a mesh-by-meshbasis, as in the case of above-mentioned Embodiments 1 and 2.

Next, the operation of the map information processor in accordance withEmbodiment 3 of the present invention configured as mentioned above willbe explained. A map image generating process carried out by the mapinformation processor in accordance with this Embodiment 3 is the sameas that carried out by the map information processor in accordance withEmbodiment 1, except for a process of drawing point information which isperformed in step ST8 of the flow chart shown in FIG. 6. Hereafter, onlya part different from that shown in Embodiment 1 will be explained.

FIG. 13 is a flow chart showing the details of the process of drawingpoint information performed in step ST8. In this process of drawingpoint information, steps ST31 to ST36 are added to the process ofdrawing point information shown in the flow chart of FIG. 8, which iscarried out by the map information processor in accordance withEmbodiment 1, and step ST13 is replaced by step ST37. Hereafter, thesteps in which the same process as that of drawing point information inthe map information processor in accordance with Embodiment 1 is carriedout are designated by the same reference characters as those used inFIG. 8, and the explanation of the steps will be simplified.

In the process of drawing point information, it is checked to see firstwhether in-mesh image information 43 exists in the mesh-by-mesh mapinformation 31 which is the target for processing (step ST31). Morespecifically, the navigation processing unit 15 refers to the contentsof the RAM 14 to check to see whether in-mesh image information 43exists in the yet-to-be-processed mesh-by-mesh map information 31selected in step ST4.

When it is judged in this step ST31 that in-mesh image information 43exists in the mesh-by-mesh map information 31 which is the target forprocessing, the in-mesh image information 43 of the mesh-by-mesh mapinformation 31 which is the target for processing is then set as imageinformation to be searched (step ST32). More specifically, when judgingthat in-mesh image information 43 exists in the mesh-by-mesh mapinformation 31, the navigation processing unit 15 sets the in-mesh imageinformation 43 as image information to be searched. After that, thesequence advances to step ST11.

In contrast, when it is judged in step ST31 that no in-mesh imageinformation 43 exists in the mesh-by-mesh map information 31 which isthe target for processing, mesh-by-mesh map information in an upperlayer corresponding to the mesh-by-mesh map information 31 which is thetarget for processing is specified (step ST33). More specifically, thenavigation processing unit 15 specifies mesh-by-mesh map information 31included in the map display information 23 in an upper layer above thelayer in which the mesh-by-mesh map information 31 which is beingcurrently set as the target for processing is located. This process ofspecifying the mesh-by-mesh map information 31 in the upper layer willbe explained below in detail.

It is then checked to see whether or not the mesh-by-mesh mapinformation 31 in the upper layer specified in step ST33 has been readinto the RAM 14 (step ST34). More specifically, the navigationprocessing unit 15 checks to see whether or not the mesh-by-mesh mapinformation 31 in the upper layer is stored in the RAM 14. When it isjudged in this step ST34 that the mesh-by-mesh map information 31 in theupper layer has not been read into the RAM 14, the mesh-by-mesh mapinformation 31 in the upper layer is read into the RAM 14 (step ST35).More specifically, the navigation processing unit 15 reads themesh-by-mesh map information 31 in the upper layer from the HDD 13, andstores the mesh-by-mesh map information in the RAM 14. In contrast, whenit is judged in step ST34 that the mesh-by-mesh map information 31 inthe upper layer has been read into the RAM 14, the process of step ST35is skipped.

The in-mesh image information 43 of the mesh-by-mesh map information 31in the upper layer is then set as the image information to be searched(step ST36). More specifically, the navigation processing unit 15 setsthe in-mesh image information 43 of the mesh-by-mesh map information 31in the upper layer stored in the RAM 14 as the image information to besearched. After that, the sequence advances to step ST11.

It is checked to see in step ST11 whether or not one or moreyet-to-be-processed point data 61 are included in the point information53. When it is judged in this step ST11 that there is noyet-to-be-processed point data 61, the process of drawing the pointinformation is ended. In contrast, when it is judged that one or moreyet-to-be-processed point data 61 are included in the point information,one of the one or more yet-to-be-processed point data 61 is thenselected as the target for processing (step ST12).

Image data whose identifier 111 matches the image code 73 of one pointdata 61 which is the target for processing is then searched from amongthe image information to be searched (step ST37). More specifically, thenavigation processing unit 15 searches through the image information tobe searched stored in the RAM 14 for image data 112 having an identifier111 which matches the image code 73 of one yet-to-be-processed pointdata 61 included in the point information 53 of the mesh-by-mesh mapinformation 31.

It is then checked to see whether or not the image data exists (stepST14). When it is judged in this step ST14 that the image data 112exists, the image data 112 is then drawn according to the coordinateinformation 71 of the point data 61 (step ST15). In contrast, when it isjudged in step ST14 that the image data does not exist, image data 92whose identifier 91 matches the category code 72 of the point data 61selected in step ST12, which is the target for processing, is searchedfrom among the image information 22 (step ST16).

It is then checked to see whether or not the image data exists (stepST17). When it is judged in this step ST17 that the image data does notexist, the sequence returns to step ST11 and the above-mentionedprocesses are repeated. In contrast, when it is judged in step ST17 thatthe image data 92 exists, the image data 92 is then drawn according tothe coordinate information 71 of the point data 61 (step ST18). Afterthat, the sequence returns to step ST11 and the above-mentionedprocesses are repeated.

Next, the process of specifying the mesh-by-mesh map information in theupper layer corresponding to the mesh-by-mesh map information which isthe target for processing, which is carried out in step ST33, will beexplained with reference to FIG. 14. In the layered pieces of mapdisplay information arranged in a hierarchical format, map displayinformation in a lower layer has finer meshes than those of map displayinformation in an upper layer. This is because mesh-by-mesh mapinformation in a lower layer is stored more densely than that in anupper layer. In this example shown in FIG. 14, meshes 11, 12, 13 and 14in a lower layer correspond to a mesh 21 in an upper layer.

As previously explained, because the map information processor inaccordance with Embodiment 3 of the present invention is configured insuch a way as to include layered pieces of map display informationarranged in a hierarchical format, the map information processorprovides the same advantages as those provided by the map informationprocessor in accordance with above-mentioned Embodiment 1 or Embodiment2 while suppressing the volume of data stored in the HDD 13.

The map information processor in accordance with Embodiment 3 isconfigured in such a way as to acquire image data 112 corresponding toan image code 73 from either the in-mesh image information 43 includedin the mesh-by-mesh map information 31 which is the target forprocessing or the in-mesh image information 43 included in themesh-by-mesh map information which is located in an upper layerimmediately above the mesh-by-mesh map information 31 which is thetarget for processing and which corresponds to the mesh-by-mesh mapinformation 31. As an alternative, the map information processor inaccordance with Embodiment 3 can be configured in such a way as toacquire image data 112 corresponding to an image code from the in-meshimage information 43 included in the mesh-by-mesh map information in anupper layer which is located two or more layers above the mesh-by-meshmap information 31 which is the target for processing and whichcorresponds to the mesh-by-mesh map information 31.

The map information processor in accordance with Embodiment 3 canarrange image data managed with the in-mesh image information 43 storedin the HDD13 in order based on layers used, and the navigationprocessing unit 15 can change image data 112 used for an map image whichis generated on the basis of in-mesh image information 43 in a lowerlayer in such a way as to continuously acquire the image data 112 in theorder in which the image data 112 are arranged when acquiring in-meshimage information in an upper layer corresponding to the in-mesh imageinformation 43 in a lower layer.

FIG. 15 shows the data structure of in-mesh image information 43 forused in a map information processor in accordance with a variant of thisEmbodiment 3. The in-mesh image information 43 is comprised of a set ofimage records 101 ₁, 101 ₂, . . . , and 101 _(n) arranged in order basedon layers used, and layer-by-layer image management information 102, asshown in FIG. 15( a). The layer-by-layer image management information102 is comprised of a row of layer-by-layer image management records 103₁, 103 ₃, . . . , and 103 _(n) (each layer-by-layer image managementrecord is representedly designated by a numeral reference “103” fromhere on), shown in FIG. 15( b). As shown in FIG. 15( c), eachlayer-by-layer image management record is comprised of a starting recordnumber 104 and a use record count 105, and they are used to specify animage record used in each layer.

In a case in which the in-mesh image information 43 having such a datastructure as mentioned is used in order to generate a map image based onlayer-by-layer map display information 23 having three layers, threelayer-by-layer image management records are generated in thelayer-by-layer image management information 102. When the startingrecord number is “1” and the use record count is “2” in the firstlayer-by-layer image management record, it is assumed that the imagerecord which is the second one counted from the first image record, i.e.the second image record is used. When the starting record number is “1”and the use record count is “5” in the second layer-by-layer imagemanagement record, it is assumed that the image record which is thefifth one counted from the first image record, i.e. the fifth imagerecord is used.

The map information processor in accordance with the variant of thisEmbodiment 3 can shorten the time required to perform a map imagegenerating process. The map information processor in accordance with thevariant of this Embodiment 3 can be alternatively configured in such away as to, instead of specifying an image record to be are used for eachof layers, specify an image record to be used according to a map displayscale.

INDUSTRIAL APPLICABILITY

As mentioned above, the map information processor in accordance with thepresent invention is configured in such a way as to generate a map imageon the basis of image data included in in-mesh image information managedon a mesh-by-mesh basis in order to shorten the time required to performa map image generating process, and the data structure of mapinformation in accordance with the present invention is configured insuch a way that a map image is generated on the basis of image dataincluded in in-mesh image information managed on a mesh-by-mesh basis inorder to shorten the time required for the map information processor toperform a map image generating process. Therefore, generation of a mapimage can be implemented in a short time, and the map informationprocessor and the data structure of map information in accordance withthe present invention are suitable for use in a car navigation deviceand so on.

The invention claimed is:
 1. A map information processor comprising: amap information storage unit for storing map display informationincluding a set of mesh-by-mesh map information elements managed on amesh-by-mesh basis, each mesh-by-mesh map information element includingrespective sub-elements storing road information, background informationfor a corresponding mesh, and in-mesh image information for acorresponding mesh, the map information storage unit further storingimage information which is managed outside of the map displayinformation; an image processing unit for generating a map image on abasis of image data included in each road information sub-element,background information sub-element, and in-mesh image informationsub-element included in the mesh-by-mesh map information read from saidmap information storage unit, the image processing unit generating themap on further basis of image data included in the image informationwhich is managed outside of the map display information and is read fromthe map information storage unit; and a display unit for displaying themap image generated by said image processing unit, wherein the imageinformation which is managed outside of the map display information isstored in the map storage unit in a data structure that is not arrangedon a mesh-by-mesh basis.
 2. The map information processor according toclaim 1, wherein the map information stored in the map informationstorage unit is divided into a plurality of pieces of map informationhierarchically organized, and the image processing unit acquires theimage data for use in the map image which the image processing unitgenerates on a basis of mesh-by-mesh map information in a lower layerfrom in-mesh image information included in mesh-by-mesh map informationin an upper layer corresponding to said mesh-by-mesh map information inthe lower layer.
 3. The map information processor according to claim 2,wherein the image data managed with the in-mesh image information storedin the map information storage unit are arranged in order based onlayers in which the image data are used, and the image processing unitcontinuously acquires the image data for use in the map image which theimage processing unit generates on a basis of the mesh-by-mesh mapinformation in a lower layer in order in which the image data arearranged when acquiring the in-view image information included inmesh-by-mesh map information in an upper layer corresponding to themesh-by-mesh image information in a lower layer.
 4. The map informationprocessor according to claim 1, wherein the point information indicateswhether image data of each map symbol and/or facility mark is storedwithin an in-mesh image information sub-element of the mesh-by-mesh mapinformation element or within image information data managed outside ofthe set of mesh-by-mesh map information elements.
 5. The map informationprocessor according to claim 1, wherein the background informationsub-element of each mesh-by-mesh map information element stores pointinformation for each map symbol and/or facility mark associated with thecorresponding mesh.
 6. The map information processor according to claim5, wherein said point information includes coordinate information fordetermining a position within the corresponding mesh at which each mapsymbol and/or facility mark is placed, an image code for specifyingimage data for each map symbol and/or facility mark included in acorresponding in-mesh information sub-element, and a category code forspecifying image data for each map symbol and/or facility mark includedin the image information data managed outside of the set of mesh-by-meshimage information elements, and the image processing unit acquires theimage data for each map symbol and/or facility mark, on the basis of theimage code, from the appropriate one of the in-mesh image informationsub-element and the image information managed outside of the set ofmesh-by-mesh map information elements.
 7. The map information processoraccording to claim 6, wherein the point information further includespriority information for determining a priority for displaying the imageshown by the image data for each map symbol and/or facility mark, andthe image processing unit determines an image to be included in the mapimage generated thereby according to said priority information.
 8. Themap information processor according to claim 7, wherein the imageprocessing unit acquires the image data corresponding to the image codeaccording to the priority information, and generates the map imageincluding the image shown by this acquired image data.
 9. The mapinformation processor according to claim 1, wherein the in-mesh imageinformation and the image information which is managed outside of themap display information contain image data in a bitmap format.
 10. Themap information processor according to claim 1, wherein a data structurein which the image information which is managed outside of the mapdisplay information is stored contains a set of image records, eachcontaining image data in a bitmap format and a corresponding identifier,wherein a location in the map image in which one of the image data is tobe displayed is determinable by a code in the background informationsub-element of one of the mesh-by-mesh information elements which linksthe identifier corresponding to the one of the image data to the meshcorresponding to the one of the mesh-by-mesh information elements.
 11. Anon-transitory computer readable medium on which is stored mapinformation comprising: map display information comprised of a set ofmesh-by-mesh map information elements managed on a mesh-by-mesh basis,each mesh-by-mesh map information element including respectivesub-elements storing road information, background information, andin-mesh image information for a corresponding mesh; and imageinformation which is managed outside of the map display information,wherein the image information which is managed outside of the mapdisplay information is stored in a data structure that is not arrangedon a mesh-by-mesh basis.
 12. The computer readable medium on which isstored the map information according to claim 11, wherein the mapinformation is divided into a plurality of pieces of map informationhierarchically organized in such a way that image data corresponding toa map image based on mesh-by-mesh map information in a lower layer isincluded in in-mesh image information included in mesh-by-mesh mapinformation in an upper layer corresponding to said mesh-by-mesh mapinformation in a lower layer.
 13. The computer readable medium on whichis stored the map information according to claim 12, wherein image datamanaged with the in-mesh image information are arranged in order basedon layers in which the image data are used.
 14. The non-transitorycomputer readable medium according to claim 11, wherein the pointinformation indicates whether image data of each map symbol and/orfacility mark is stored within an in-mesh image information sub-elementof the mesh-by-mesh map information element or within image informationdata managed outside of the set of mesh-by-mesh map informationelements.
 15. The non-transitory computer readable medium according toclaim 11, wherein the background information sub-element of eachmesh-by-mesh map information element stores point information for eachmap symbol and/or facility mark associated with the corresponding mesh.16. The computer readable medium on which is stored the map informationaccording to claim 15, wherein said point information includescoordinate information for determining a position within thecorresponding mesh at which each map symbol and/or facility mark isplaced, an image code used for acquiring image data of each map symboland/or facility mark included in a corresponding in-mesh imageinformation sub-element, and a category code used for acquiring imagedata of each map symbol and/or facility mark included in the imageinformation managed outside of the mesh-by-mesh map informationelements.
 17. The computer readable medium on which is stored the mapinformation according to claim 16, wherein the point information furtherincludes priority information for determining a priority for displayingthe image shown by the image data for each map symbol and/or facilitymark.
 18. The non-transitory computer readable medium according to claim11, wherein the in-mesh image information and the image informationwhich is managed outside of the map display information contain imagedata in a bitmap format.
 19. The non-transitory computer readable mediumaccording to claim 11, wherein a data structure in which the imageinformation which is managed outside of the map display information isstored contains a set of image records, each containing image data in abitmap format and a corresponding identifier, wherein a location in themap image in which one of the image data is to be displayed isdeterminable by a code in the background information sub-element of oneof the mesh-by-mesh information elements which links the identifiercorresponding to the one of the image data to the mesh corresponding tothe one of the mesh-by-mesh information elements.